1. Field of the Disclosure
Embodiments disclosed herein relate generally to a process for the conversion of tertiary butyl alcohol (TBA) to ethyl tertiary butyl ether (ETBE). More specifically, embodiments disclosed herein relate to the dehydration of TBA to isobutylene, which is subsequently reacted with ethanol to form ETBE.
2. Background
Various commercial processes for the production of propylene oxide include the reaction of propylene with tertiary butyl hydroperoxide, resulting in the formation of propylene oxide and TBA. See, for example, U.S. Pat. Nos. 7,223,875 and 5,424,458.
In order for the propylene oxide process to be economical, a good value for the TBA must be realized. Conversion of the TBA to a high-octane gasoline blendstock may allow for the needed TBA value to be realized.
For example, U.S. Pat. No. 5,424,458 discloses that the TBA can be dehydrated to isobutylene. The isobutylene may then be converted in an existing etherification unit to methyl tertiary butyl ether (MTBE). Alternatively, the TBA may be reacted directly in the etherification unit with methanol to form MTBE in a one-step etherification reaction, such as those disclosed in U.S. Pat. Nos. 5,716,896 and 5,527,970.
U.S. Pat. Nos. 5,849,971 and 5,811,620 disclose processes for dehydration of TBA using reactive distillation. U.S. Pat. No. 5,637,777 discloses a catalytic distillation process for preparing tertiary alkyl ethers from isoolefins. Other processes for preparing tertiary alkyl ethers are disclosed in, for example, U.S. Pat. Nos. 5,292,964, 5,248,836, 5,231,234, and 4,935,552.
Some of the above described processes require additional separation steps which may add significantly to operating and capital expenditures. For example, one-step etherification of TBA may result in the formation of a water-ETBE azeotrope, and water may also form an azeotrope with any unreacted ethanol. The formation of these azeotropes may add to the difficulty and expense of recovering a high purity ETBE product.
Accordingly, there exists a need for an efficient process for the conversion of TBA to ETBE.